The purpose of this study is to determine whether Continuous Positive Airways Pressure (CPAP) improves quality of life, cardiovascular (blood pressure) and metabolic profile (glucose and lipid metabolism) in females with moderate-to-severe Obstructive Sleep Apnea (OSA).

Study Design: multicenter, open-label, randomized, controlled trial of parallel groups with a final blind evaluation.

Study sites. The following hospitals will participate in the study: Valme (Sevilla), la Fe (Valencia), Virgen del Rocío (Sevilla), Gral Yagüe (Burgos), San Pedro de Alcántara (Cáceres), Dr Peset (Valencia), Severo Ochoa (Madrid), Reina Sofía (Córdoba), Dr Negrín (Las Palmas de Gran Canaria), Virgen de la Victoria (Málaga), Río Hortega (Valladolid), Costa del Sol (Málaga), Marqués de Valdecilla (Santander), Albacete (Albacete), Virgen del Puerto (Cáceres), Puerta de Hierro (Madrid), Consorcio Sanitario de Terrassa (Barcelona), Getafe (Madrid), Gral de Alicante (Alicante), Morales Meseguer (Murcia), Tomelloso (Ciudad Real), and Fundación Jiménez Díaz (Madrid). All centers from Spain.

Methods: consecutive outpatient women aged 18-75 years and referred to the sleep clinics for suspicion of OSA will be studied. They will undergo a diagnostic home respiratory polygraphy, and those diagnosed with moderate-to-severe OSA (AHI ≥15) will be eligible for this study and randomized to optimal CPAP treatment or conservative treatment for 12 weeks. Every women will fulfill a standardized protocol and different quality of life questionnaires. Office blood pressure will be measured. Fasting blood samples will be collected to assess glucose and lipid metabolism. All the measurements will be performed at baseline and after 12 weeks of follow-up. Women will be examined at the time of inclusion, after 4 weeks of follow-up and at the end of follow-up (12 weeks).

149 women with moderate-to-severe OSA need to be enrolled in each study arm, according to the sample size calculated to achieve a clinically significant improvement in the Quebec Sleep Questionnaire. The results will be analyzed both on an intention-to-treat basis and on a per-protocol basis (data only from patients who finish the study and show good adherence to CPAP, defined as an average objective use of at least 4 hours/day).

Inclusion Criteria:

• Moderate-to-severe OSA (Apnea-Hypopnea index ≥15) diagnosed by Home Respiratory Polygraphy.
• Age between 18-75 years.

Exclusion Criteria:

• diagnosis of narcolepsy or restless legs syndrome
• unstable cardiovascular profile (cardiovascular event in the previous 3 months)
• cancer or life expectancy lower than 1 year
• uncontrolled psychiatric disorders
• central sleep apnea (>50% of central events)
• pregnancy
• risky jobs and severe hypersomnolence (Epworth >=18) requiring urgent treatment
• either respiratory failure (SaO2<90% or partial oxygen pressure [pO2] <60 mmHg or Long-term O2 therapy
• heart failure (New York Heart Association class III-IV)
• prior CPAP therapy